1. Field of the Invention
The present invention relates to an electric connector used mainly for high-speed digital signaling and capable of providing good impedance matches.
2. Description of the Related Art
In a known electric connector of this type, an insulative body has groups of contacts disposed in two rows along its width, and the groups of contacts are arranged in a zigzag manner. The groups of contacts include ground contacts and pairs of signal contacts to serve as differential pairs for high-speed digital signaling.
Some of the ground contacts are wider than some of the signal contacts making up a pair, and each of the ground contacts is arranged so that their widthwise ends overlaps widthwise ends of each pair of signal contacts in plain positions. With this structure, impedance is matched within each differential pair of contacts and among the differential pairs of contacts (see Japanese Published Patent Publication No. 2003-505826, which is the translation of Published International Application No. WO01/006602).
However, as to a differential pair located at an outermost end of the groups of contacts, there is no ground contact disposed at one side of a signal contact of the differential pair. Therefore, capacitance of this signal contact with respect to a ground contact is smaller as compared with that of the other signal contact of the same differential pair, with the result of increased impedance. For this reason, there are impedances mismatches between the contacts, thereby degrading transmission characteristics of the connector.
In this case, it is not impossible to improve impedance matching by disposing a dummy ground contact at the side of the signal contact in question or by bringing a portion of a shield cover of the electric connector close to the signal contact. However, the addition of a dummy ground contact or the change in shape of the shield cover will cause increase in the number of components and assembly steps, leading to increased costs.